"He went to the mountain alone without a guide at 06:00 and aspired to climb it in one day," Miss Baughan said.

Image copyrightBluebell BaughanImage caption
The pair were two-and-a-half months into a four-month trip they had been saving for

She was in touch with Mr Webb by phone when he informed her he had fallen and could not find his way back to the trail.

'Cold and wet'

"He was sure he could make it back but by nightfall it was apparent he wasn't going to," she said.

"Aiden said a rock had cut his arm open and he had hurt his knee. We were in touch all night.

"He said no-one would be able to find him, but by 6am on Saturday he finally agreed to me getting help."

Image caption
Mr Webb was trekking alone on Fansipan mountain when he fell down a ravine

Miss Baughan, who is helping co-ordinate the search from the town of Sa Pa, said rescuers had been on the mountain since Saturday morning.

"Thirty-two men spent last night on the mountain, a mixture of military police, forestry workers and local police.

"There is only one police officer here in Sa Pa who speaks English, but everyone has been very helpful," she said.

Fansipan mountain

Image copyrightBluebell Baughan

Located in the Lao Cai Province in north-west Vietnam

At 10,312 ft (3,143m) above sea level, it is the highest peak in Indochina (Vietnam, Laos and Cambodia)

Known as the Roof of Indochina, it is a popular eco-tourist spot in the region

Organised hikes to the summit usually take two to three days

The nearest town, Sa Pa, is five-and-a-half miles (9km) away

Miss Baughan said conditions on the mountain were "very cold and wet".

"Aiden is a very good climber, but he is injured," she said.

Image copyrightBluebell BaughanImage caption
Mr Webb, pictured with Miss Baughan, graduated with a BA Hons in Drama from Anglia Ruskin University in Cambridge in 2014

Mr Webb's father and uncle are expected to arrive in Vietnam this evening although they will not reach the north until Tuesday.

A Foreign and Commonwealth Office spokeswoman said: "We are supporting the family of Aiden Webb, a British man reported missing in Vietnam. We are working closely with the local authorities leading the search."